The present disclosure relates to a battery remaining amount detection unit, an electric vehicle, and an electric power supply unit.
Secondary batteries that are repeatedly chargeable and dischargeable, for example, lithium-ion secondary batteries are widely used as power sources in a field of power of electric vehicles, hybrid vehicles, electric motorcycles, electrically-assisted bicycles, and the like, and a field of storage for load leveling, peak shift, backup, and the like.
When a battery is used, an electric charge in the battery is discharged to reduce a remaining amount of the battery; therefore, it is necessary to charge the battery at some point. When the battery is continuously used under a state in which the remaining amount of the battery (hereinafter referred to as “remaining amount”, as necessary) is reduced, a failure of or damage to the battery may result to cause an accident. Moreover, in a case where the battery is used as power of an electric car, if the remaining amount is not accurately kept track of, the battery may suddenly run out to put the electric car out of action. Therefore, it is extremely important to accurately keep track of the remaining amount.
As a method of keeping track of the remaining amount, a method of integrating an electric current when a battery is charged and discharged with use of an electric current measurement unit such as a coulomb meter is known.
As another method, as described in Japanese Unexamined Patent Application Publication (Published Japanese Translation of PCT Application) No. 2010-523971, a method of calculating a remaining amount of a battery from an open-circuit voltage of the battery is proposed.